November 30 , 2016:

by Raphael Rosen

In 2006, fossil collector Clayton Phipps (a Montana rancher known as the “Dinosaur Cowboy”) and his crew discovered a rare fossil on private land in Montana’s Hell Creek Formation: the bones of two fully articulated dinosaurs that appeared to have died together, locked in battle. The fossil duo — a small, pony-sized carnivorous tyrannosaurid and a slightly larger herbivorous ceratopsian, both now preserved in plaster — became known as the “Montana Dueling Dinosaurs.”

Last November, the fossils were put on the block at Bonhams auction house in New York City — but they did not sell. Had the set fetched the nearly $9 million it was expected to, it would have set a record for a fossil sale.

The claws on the Nanotyrannus specimen are twice the size of a fully grown T. rex’s claws despite it being less than half the size of a full-size T. rex. Credit: Raphael Rosen.

The highest bid, which came in at $5.5 million, did not meet the reserve price. Nevertheless, a Bonhams director expects the set will eventually be sold. “There’s still activity behind the scenes,” says Thomas Lindgren, co-consulting director of Bonhams’ natural history department.

For now, the Dueling Dinosaurs remain locked in an unidentified warehouse somewhere in the United States — along with any scientific information the unique specimens may reveal.

Limited research so far indicates that the pair seems to have died together, perhaps in a battle. Several of the carnivore’s teeth, for instance, broke off in the herbivore’s body: one in a vertebra in the ceratopsian’s back and another near the victim’s neck. But the ceratopsian got in a couple of hits too: The tyrannosaurid’s skull and chest are caved in.

The fossils are quite unusual in that they are completely articulated, meaning that they were found in their natural positions. “This is almost unheard of in nature,” Lindgren says. “When a dinosaur dies, most of the time raptors and other carnivores come in and pick the bones clean and rip the dinosaur apart. Rarely do you find articulated specimens unless they were buried exceptionally quickly.”

Rib bones of one of the species of the Dueling Dinosaurs. Credit: Raphael Rosen.

The Dueling Dinosaurs are astonishing for another reason, Lindgren says: Both the tyrannosaurid and the ceratopsian fossils are almost 100 percent complete. Lindgren says that is because they were preserved in “unconsolidated sandstone,” which usually forms from sand with high water content. One hypothesis, therefore, is that while the two dinosaurs were fighting on watery sand, an earthquake struck. “In a major event like that,” Lindgren says, “the sand becomes liquefied and it just sucked the dinosaurs down in and covered them quickly” — like quicksand.

Other hypotheses about these dinosaurs abound — including about what species they are — but unfortunately, because the fossils were excavated privately (not by paleontologists) and because they are privately for sale, these hypotheses can’t be tested.

“A basic tenet of science is that claims must be testable and falsifiable,” says Tyler Lyson, a postdoctoral fellow in paleontology at the Smithsonian Institution’s National Museum of Natural History. “If the specimen is in private hands, then there is always the possibility of the specimen not being accessible to scientists. It might belong to someone right now who is open to having people study it, but that could easily change with the next owner. So in general, specimens in private hands are off-limits to scientists, in terms of publications.”

Unless the Dueling Dinosaurs are made more available — perhaps through donation to a museum by their eventual owners — the fossils’ secrets will most likely remain hidden.

Some important scientific evidence has already been permanently lost, simply because the fossil was not collected by scientists.

“From my perspective, these fossils have no scientific value,” says Jack Horner, a paleontologist at Montana State University. “They were collected without scientific evaluation of the site, its sedimentology, stratigraphy or taphonomy. They were simply collected for the purpose of making as much money as possible.”

Also, paleontologists have not yet been able to confirm exactly what species the fossils represent. Based on analysis by paleontologist Peter Larson, president of the Black Hills Institute of Geological Research, Inc., who now has stewardship of the fossil, the tyrannosaurid in the Dueling Dinosaurs set has been tentatively identified as Nanotyrannus rex. If confirmed, it would be just the second ever identified, and could help paleontologists determine whether Nanotyrannus was its own species or a juvenile T. rex.

There are more clues in the fossil’s skull. The Nanotyrannus has 16 to 18 tooth sockets in its upper jaw, whereas T. rex has only 11 to 12 sockets. Although animals may lose teeth as they age, they usually don’t lose fundamental anatomical features like tooth sockets. To some paleontologists, this evidence points squarely in one direction: “This is a valid species,” Lindgren says.

In the end, until scientists can fully examine these specimens and the area from which they were uncovered, Horner says, “a person cannot say for sure that the meat-eater is a possible Nanotyrannus, a juvenile T. rex, or some other taxon.”

The ceratopsian is significant in its own right. “There are indications on [the ceratopsian’s] skull and possibly in the pelvic area that this may actually be a new species,” Lindgren says. For instance, the fossil has short, stubby horns, whereas Triceratops — another member of the fossil’s taxonomic family — has horns that are much longer. The ceratopsian also has horns projecting from the orbital bones near its eyes, a feature never observed before in dinosaurs in its family.

For now, the fossils are in paleontological limbo. They are currently in storage, under Larson’s stewardship, and to maintain security, the location of the storage facility cannot be revealed. A major American museum is in negotiations to acquire the fossils, but the price has not yet been determined. “Hopefully, something will happen in a month or two,” Larson says.

“I feel confident that we’ll find a home for these dinosaurs,” Lindgren says. Meanwhile, the “answers to many scientific inquiries,” Lindgren says, “are right here within these plaster jackets.”